Hearst has also threatened to shutter the Seattle Post-Intelligencer unless a buyer emerged -- and none has. The Tribune Co. filed for bankruptcy protection in December. Owners of the Daily News and Philadelphia Inquirer have also sought protection in bankruptcy court, the News reported.

The Chronicle lost $50 million in 2008 and has posted major losses, since 2001, Hearst said in a statement.

San Francisco Mayor Gavin Newsom said in a statement he was concerned but optimistic the paper could be saved.

We don't want to see this cherished institution close its doors, the statement from the mayor's office said.